Re: [PATCH 2/2] configs: Add generic qcom_tfa_optee_defconfig

Neil Armstrong
2026-01-15T13:03:38Z

On 1/15/26 13:25, Sumit Garg wrote:
> + Jens (OP-TEE driver author in U-Boot)
>
> On Thu, Jan 15, 2026 at 11:49:49AM +0100, neil.armstrong@linaro.org wrote:
>> On 1/15/26 07:10, Sumit Garg wrote:
>>> On Wed, Jan 14, 2026 at 03:56:02PM +0100, Casey Connolly wrote:
>>>>
>>>>
>>>> On 09/01/2026 12:02, Sumit Garg wrote:
>>>>> On Thu, Jan 08, 2026 at 05:41:42PM +0100, Casey Connolly wrote:
>>>>>>
>>>>>>
>>>>>> On 29/12/2025 12:43, Sumit Garg wrote:
>>>>>>> From: Sumit Garg <sumit.garg@oss.qualcomm.com>
>>>>>>>
>>>>>>> Recently upstream TF-A/OP-TEE has started gaining support for Qcom
>>>>>>> platforms. RB3Gen2 being the first one and more to come. U-Boot in
>>>>>>> corresponding boot flow is packaged as a position independent executable.
>>>>>>>
>>>>>>> So, lets add a generic U-Boot defconfig for Qcom platforms to support
>>>>>>> TF-A/OP-TEE based TrustZone stack. Build command:
>>>>>>>
>>>>>>> $ make qcom_tfa_optee_defconfig
>>>>>>> $ make -j`nproc` DEVICE_TREE=qcom/qcs6490-rb3gen2
>>>>>>
>>>>>> This would be better suited as a config fragment rather than a new
>>>>>> defconfig imo.
>>>>>
>>>>> That's fine with me to add it as a config fragment.
>>>>>
>>>>>>
>>>>>> But more importantly, enabling OPTEE support in U-Boot doesn't imply
>>>>>> that it will be used, just that it's supported.
>>>>>
>>>>> There are real use-cases of OP-TEE in U-Boot for Qcom platforms like
>>>>> secure EFI variables based on OP-TEE secure storage. Have a look here [1].
>>>>>
>>>>> And sure there will be more such use-cases like fTPM, KASLR etc. can be
>>>>> supported based on OP-TEE.
>>>>
>>>> I was referring literally to the fact that CONFIG_OPTEE being enabled
>>>> doesn't imply that OP-TEE is running, it's faulty logic to assume that's
>>>> the case and add nodes to the DT.
>>>
>>> I don't disagree here as having a runtime check is always a better
>>> choice then a compile time config option. However, there isn't a common
>>> info method from properietary firmware that says if QTEE is running
>>> instead of OP-TEE.
>>>
>>>>
>>>> I just checked and there is an SMC call that tells you the UUID for the
>>>> trusted OS, referred to as OPTEE_SMC_CALL_GET_OS_UUID in U-Boot and
>>>> OPTEE_ABI_CALL_GET_OS_UUID in OP-TEE. Presumably this identifies OP-TEE
>>>> specifically.
>>>
>>> Also, we don't know how the QTEE will react to this OP-TEE specific SMC
>>> call given it's different variants running on legacy and the newer SoCs.
>>> So I would suggest to better gate OP-TEE presence behind a compile time
>>> check only.
>>
>> So you say it's fine to add the optee node, and the driver will bail out if
>> OPTEE is not present, but it's not good to call OPTEE_SMC_CALL_GET_OS_UUID
>> in the fixup code to enable OPTEE only if present ?
>>
>> It's literally the same, my point in https://lore.kernel.org/all/b60d5ee7-fa27-4dc1-8a09-964912ec5654@linaro.org/
>> was exactly that, just call OPTEE_SMC_CALL_GET_OS_UUID and add the OPTEE
>> node only if present _AND_ if CONFIG_OPTEE is enabled.
>>
>> Move the CONFIG_OPTEE enable in a fragment and we're done, you will only
>> select OPTEE explicitly on desired platforms, and won't run the naughty
>> OPTEE_SMC_CALL_GET_OS_UUID on old crappy platforms.
>
> I am still trying to understand what benefit does invoking
> OPTEE_SMC_CALL_GET_OS_UUID from platform code provides us. Surely it
> can't be used to detect OP-TEE not present when QTEE is running due to
> unknown behaviour with QTEE.

Sorry but what exactly do you expect that will happen if you enable the OPTEE
driver when running with QTEE ?

>
> Jens,
>
> Will it be fine with you to expose is_optee_api() from the OP-TEE driver
> for the platform code to invoke it independently? Just for the sake of this
> discussion in case people still insist on it being the right thing to do.
>
> -Sumit
>
>>
>> Neil
>>
>>>
>>>>
>>>> My suggestion would be to make this SMC call if CONFIG_OPTEE is enabled
>>>> in qcom_psci_fixup(), compare the UUID and add the node if it matches.
>>>
>>> That's exactly the first SMC call that U-Boot and Linux OP-TEE driver
>>> does to compare the UUID here [1] and bail out of the driver. I don't
>>> see a value of a redundant invoke in the Qcom specific platform code.
>>>
>>> [1] drivers/tee/optee/core.c:823: if (!is_optee_api(pdata->invoke_fn))
>>>
>>> -Sumit
>>>
>>>>
>>>>>
>>>>> [1] lib/efi_loader/efi_variable_tee.c
>>>>>
>>>>>>
>>>>>> So I think the more appropriate patch here would be to just enable
>>>>>> OP-TEE in qcom_defconfig (assuming the binary size isn't significantly
>>>>>> affected).
>>>>>
>>>>> The OP-TEE driver in U-Boot itself is probed based on DT and it's not
>>>>> only specific to Qcom platforms but every other platform using OP-TEE.
>>>>>
>>>>>>
>>>>>> Considering the other patch is based on this assumption that if OP-TEE
>>>>>> support is enabled then the board must be using it, a different approach
>>>>>> is definitely needed.
>>>>>
>>>>> Yeah that's true even with TF-A boot flow, there is possibility to boot
>>>>> without OP-TEE as well. However, TF-A generally doesn't provide a
>>>>> generic option to detect whether OP-TEE is running or not.
>>>>>
>>>>>>
>>>>>> When I was looking into this last year I remember discussing this same
>>>>>> issue from the Linux side, there is a good argument to be made that
>>>>>> OP-TEE support in Linux shouldn't be based on the devicetree -
>>>>>> particularly in the Qualcomm case where whether or not OP-TEE is used is
>>>>>> a simple software change, nothing to do with hardware.
>>>>>
>>>>> Sadly it's true for every other silicon vendor too. But OP-TEE support
>>>>> based on DT has become an ABI unless migration for OP-TEE support based
>>>>> on FF-A comes into picture.
>>>>>
>>>>>>
>>>>>> So in general I'm not particularly keen on this approach, I think it
>>>>>> /might/ be acceptable for U-Boot to have some fixup code to add the
>>>>>> OP-TEE node if OP-TEE is in use with the idea of phasing that out in
>>>>>> favour of runtime detection in the OS itself. I'd also expect that fixup
>>>>>> code to go in the generic U-Boot DT fixup code that runs before we jump
>>>>>> to the OS (like the EFI DT fixup function).
>>>>>
>>>>> The EFI DT fixup code is already there based on U-Boot DT. Have a look
>>>>> here:
>>>>>
>>>>> boot/image-fdt.c:627: fdt_ret = optee_copy_fdt_nodes(blob);
>>>>>
>>>>> In general on Arm platforms there isn't any SMC bus to detect
>>>>> dynamically if there is support for OP-TEE or not. That's why
>>>>> platform bus was choosen for the U-Boot and Linux OP-TEE driver. It's
>>>>> similar to how we have the SCM DT node for Qcom platforms.
>>>>>
>>>>> FF-A bus tries to solve that problem to unify that approach for future
>>>>> platform but U-Boot hasn't yet gained support for FF-A based OP-TEE
>>>>> driver too.
>>>>>
>>>>> Anyhow, this is the sanest way I can come up with to enable OP-TEE
>>>>> support in a general way for all the Qcom platforms. This is aligned
>>>>> with how OP-TEE support is detected for other silicon vendors too.
>>>>>
>>>>> -Sumit
>>>>>
>>>>>>
>>>>>> Kind regards,
>>>>>>
>>>>>>>
>>>>>>> For more information refer here:
>>>>>>> https://trustedfirmware-a.readthedocs.io/en/latest/plat/qti/rb3gen2.html
>>>>>>>
>>>>>>> Signed-off-by: Sumit Garg <sumit.garg@oss.qualcomm.com>
>>>>>>> ---
>>>>>>> configs/qcom_tfa_optee_defconfig | 7 +++++++
>>>>>>> 1 file changed, 7 insertions(+)
>>>>>>> create mode 100644 configs/qcom_tfa_optee_defconfig
>>>>>>>
>>>>>>> diff --git a/configs/qcom_tfa_optee_defconfig b/configs/qcom_tfa_optee_defconfig
>>>>>>> new file mode 100644
>>>>>>> index 00000000000..c398521770f
>>>>>>> --- /dev/null
>>>>>>> +++ b/configs/qcom_tfa_optee_defconfig
>>>>>>> @@ -0,0 +1,7 @@
>>>>>>> +# Configuration for building a generic U-Boot image
>>>>>>> +# with support for TF-A/OP-TEE based Arm TrustZone stack.
>>>>>>> +
>>>>>>> +#include "qcom_defconfig"
>>>>>>> +
>>>>>>> +CONFIG_TEE=y
>>>>>>> +CONFIG_OPTEE=y
>>>>>>
>>>>>> --
>>>>>> // Casey (she/her)
>>>>>>
>>>>
>>>> --
>>>> // Casey (she/her)
>>>>
>>